Project Summary/Abstract Despite numerous efforts to increase access to dental care for vulnerable groups, disparities in oral health and healthcare continue to exist. Medicaid is now the nation's largest source of health insurance coverage, and since it primarily offers insurance to low-income and disabled individuals, Medicaid is a key policy lever for addressing socioeconomic disparities in health care. The Affordable Care Act (ACA) expanded Medicaid to millions of previously ineligible adults, but only 31 states and Washington DC, have chosen to participate thus far. The goal of this proposal is to leverage the natural experiment created by ACA implementation and take advantage of state-level variation in the extent of dental care covered by Medicaid in order to assess the impact of these policies to date on oral health inequalities. As Congress continues to consider major changes to Medicaid and the ACA, the results of our analysis can offer important insights for the future of oral health inequalities. We propose a mixed-methods study, combining a quantitative component using a quasi-experimental study design and national public datasets, and a qualitative element using primary data collection to assess the impact of the ACA Medicaid expansion on oral health. This project includes four studies; during the K99 phase we propose to address the following aims: 1) To estimate the effect of Medicaid expansion under the ACA on access to and utilization of oral health services; and 2) To measure the impact of Medicaid expansion on individuals' oral health- related behaviors and race/ethnic and socioeconomic inequalities in untreated dental disease. We will then address the R00 phase through the following aims: 3) To better understand dental providers' perceptions of, attitudes toward, and experiences with Medicaid expansion and to explore ACA implementation challenges; and 4) To identify barriers to and facilitators of accessing oral health care after ACA expansion among Medicaid beneficiaries. By triangulating the views from both Medicaid providers and beneficiaries, we believe our approach will provide a more comprehensive understanding of the barriers and facilitators to ACA implementation. Findings from this study will enhance our understanding of barriers to access to oral health care that could inform future policies and interventions. Furthermore, it will aid in assessing national progress towards reducing socioeconomic and racial/ethnic disparities in access to oral health services and explore mechanisms by which health policy could impact disparities in oral health. This career development award will provide me with protected research time and thus the opportunity to expand my research skills and knowledge. I will pursue further training in health policy, econometrics and mixed-methods research through didactic courses and formal advising from my mentors, who are experts in public health, health policy, health economics, health disparities, and qualitative methods. The setting of this award is at Harvard School of Dental Medicine and Harvard School of Public Health. This rich research environment will support my development as an independent researcher.